More particularly, the invention relates to a master cylinder for motor-vehicle brakes or clutches. In fact, as is known, in motor vehicles such as, for example, motorcycles, the brake generally associated with the front wheel is operated by means of a master cylinder mounted on the handlebars in the vicinity of one of the hand grips, conventionally the right-hand hand grip of the motorcycle.
Similarly, the clutch can also be operated by means of a master cylinder mounted on the handlebars on the opposite side to the brake master cylinder, that is, on the left-hand side of the motorcycle.
A master cylinder of the type described above is generally constituted by a cylinder body in which a chamber is formed for housing a piston. When the piston is operated by the driver, it acts on a working fluid contained in the respective brake or clutch system.
The chamber is arranged in communication with a reservoir which holds the working fluid and may be formed integrally with the cylinder body or may be separate and connected thereto by an external pipe.
A master cylinder of the above-mentioned type also has a control lever which is mounted for pivoting on the cylinder body and is intended to act on the piston. This control lever faces the respective hand grip of the handlebar on which the master cylinder is mounted and is operated by the driver by being pivoted about its fulcrum. In known master cylinders, as the control lever pivots about its fulcrum, it defines a plane which generally includes the axis along which an end portion of the handlebar extends, in the region of the hand grip to be gripped by the driver. The axis along which the chamber housing the piston extends and which is also defined as the axis of the master cylinder, also lies in the said plane, or in a plane parallel thereto.
In order to make the gripping of the control lever ergonomic for the driver, this plane, which contains both the axis of the end portion of the handlebar and the axis of the cylinder, is inclined to a horizontal plane, for example, defined by the plane in which the free surface of the working fluid is disposed inside the reservoir. The extent of this inclination is about 15° downwards in the direction of travel of the vehicle, this statement meaning that a point in the plane in the vicinity of the control lever is disposed below a point in the plane in the vicinity of the end portion of the handlebar, as described more specifically below.
In the field of motor vehicles, and motorcycles in particular, there is a particular need to have an especially compact and aesthetically pleasing external design which at the same time satisfies functional needs, for example, connected with aerodynamic requirements.
From this point of view, the above-mentioned master cylinders have many disadvantages. For example, both technical and aesthetic disadvantages connected mainly with problems of space requirements are encountered in mounting these cylinders on a motor vehicle. Motor vehicles in fact have bodywork elements such as hoods, windscreens, hand guards, fairings or other components which extend up to the vicinity of the ends of the handlebars where the hand grips, the master cylinders, and generally their respective reservoirs, are positioned. In particular, in the case of cylinders in which the cylinder body and the reservoir are formed integrally, the reservoir is generally positioned above the chamber housing the piston and may even reach considerable dimensions when the master cylinder is of a size suitable for operating, for example, two brake calipers.
Since the bodywork elements have to be designed to envelop the handlebars completely, housing both the master cylinders and the reservoirs, ugly protuberances are inserted in the vicinity of the latter and, as well as affecting the appearance of the bodywork, these also affect its functional and aerodynamic aspects.
The problem upon which the present invention is based is that of proposing a master cylinder for vehicles controlled by means of handlebars which has structural and functional characteristics such as to satisfy the above-mentioned requirements and, at the same time, to overcome the disadvantages mentioned with reference to the prior art.